1. Field of the Invention
The present invention generally relates to a sealing device disposed between inner and outer races rotatable relative to each other such as, for example, between inner and outer races of a rolling bearing assembly or between inner and outer races that forms respectively a part of a rotary shaft and a part of a housing, for sealing an inner space between the outer and inner races from an external environment and, more particularly, to the sealing device for a bearing that utilizes a combination of a sealing plate such as a slinger and a sealing lip.
2. Description of the Prior Art
Hitherto, such a sealing device for an axle bearing as shown in FIG. 7 has been utilized. The sealing device 10 shown in FIG. 7 is used to seal an inner annular space between a fixed inner race and a rotatable outer race and includes an inner peripheral sealing plate 51 of a generally L-sectioned configuration and an outer peripheral sealing strip 52 of a generally L-sectioned configuration. The inner and outer peripheral sealing plates 51 and 52 are so arranged and so positioned relative to each other as to define a generally rectangular sectioned annular space therebetween. The illustrated sealing device 10 also includes an elastic strip 53 made of, for example, rubber and integrated together with the outer peripheral sealing plate 52. This elastic strip 53 has sealing lips such as a side seal lip 53a and radial seal lips 53b and 53c, all formed integrally therewith. These side seal lip 53a and the radial seal lips 53b and 53c are held in contact with a radial upright wall 51a and a cylindrical wall 51b, respectively, both forming respective parts of the inner peripheral sealing plate 51. The radial upright wall 51a of the inner peripheral sealing plate 51 extends radially outwardly from the cylindrical wall 51b so as to terminate spaced a slight distance inwardly from a cylindrical wall 52b of the outer peripheral sealing plate 52 to define a labyrinth seal 54 between the radial upright wall 51a and the cylindrical wall 52b. An outer annular surface C of the radial upright wall 51a of the inner peripheral sealing plate 51 is held in flush with an annular end face A of the elastic strip 53 on the cylindrical wall 52b of the outer peripheral sealing plate 52. It is, however, to be noted that the annular end face A is in practice represented by an annular outer end face of a portion of the elastic strip 53 that is turned around a corresponding end of the cylindrical wall 52b of the outer peripheral sealing plate 52.
On the other hand, as shown in FIG. 8, the conventional axle bearing 200 including a rotatable inner race structure and a fixed outer race structure has been known, which includes an outer race 34 having an outer peripheral surface formed integrally with a radial flange through which the axle bearing 200 is fitted to an automobile body structure, and also having an inner peripheral surface formed with dual raceways 33 and 33; an inner race assembly including inboard and outboard inner races 36 and 36 having respective raceways 35 and 35 defined therein in face-to-face relation with the dual raceways 33 and 33 in the outer race 34; respective rows of rolling elements 37 and 37 rollingly accommodated between the raceways 33 and 33 in the outer race 34 and the raceways 35 and 35 in the inboard and outboard inner races 36 and 36; and inboard and outboard sealing devices 30B and 30C for sealing an annular space delimited between the outer race 34 and the inboard and outboard inner races 36 and 36.
The rolling elements 37 are retained by a retainer 39 with a predetermined circumferential space between the neighboring rolling elements 37.
To reduce the weight of the axle bearing 200, the width of the outer race 34 as measured in a direction axially of the axle bearing 200 is chosen to be smaller than the width of the inner race assembly, that is, the total width of the paired inner races 36 and 36 also as measured in a direction axially of the axle bearing 200. The outer race 34 and the inner race assembly are so positioned relative to each other that an annular end face of the outer race 34 on an outboard side is held in flush with an annular end face of the outboard inner race 36, but the opposite annular end face of the outer race 34 on an inboard side is set back axially inwardly from an annular end face of the inboard inner race 36.
The inboard sealing device 30B includes a sealing plate 63A, which serves as a core, and a seal lip member 38 formed integrally therewith. The sealing plate 63A is mounted on a shoulder at an inner end of the outer race 34. The seal lip member 38 has an inner peripheral edge formed with bifurcated radial lips 38b and 38c that are slidingly engaged with an outer peripheral surface of an inboard end of the inboard inner race 36. The outboard sealing device 30c includes a sealing plate 63B, which serves as a core, and a seal lip member 38 formed integrally therewith. The sealing plate 63B is mounted to an inner periphery of the outer race 34. The seal lip member 38 of the outboard sealing device 30c has an inner peripheral edge formed with bifurcated radial lips 38b and 38c that are slidingly engaged with an outer peripheral surface of an outboard end of the outboard inner race 36. The radial flange 32 integral with the outer race 34 is formed with a bolt hole 44 defined therein for passage therethrough of a corresponding bolt used to secure the axle bearing 200 to a knuckle carried by the automobile body.
To further reduce the weight of the axle bearing 200, as shown in FIG. 9, in a manner similar to the opposite annular end face of the outer race 34 on an inboard side, the outboard annular end face of the outer race 34 can be set back axially inwardly from the outboard annular end face of the outboard inner race 36. In such case, the inboard and outboard sealing devices 30B and 30C may have a structure identical with each other.
In the prior art sealing device 10 shown in FIG. 7, the annular end face A of the cylindrical wall 52b of the outer peripheral sealing plate 52 and the outer annular surface C of the radial upright wall 51a of the inner peripheral sealing plate 51 are held in flush with each other in respect of the datum, that is, as a theoretically accurate geometric reference. Considering a step occurring in an actual produce between the annular end face A and the outer annular surface C, and also considering a design tolerance and a possible variation which would occur during assembly in view of the plate thickness of each of the sealing plates 51 and 52, the worst case it may occur would be that the outer annular end face C will protrude a distance outwardly, i.e., rightwards as viewed in FIG. 7, from the plane of the annular end face A.
The prior art sealing device 10 makes use of a labyrinth seal 54 as a means for avoiding ingress of muddy water in cooperation with the three seal lips 53a, 53b and 53c. This labyrinth seal 54 is formed between a free end face a of the radial upright wall 51a of the inner peripheral sealing plate 51 and an inner peripheral face b of the cylindrical wall 52b of the outer peripheral sealing plate 52.
However, if the outer annular end face C protrudes outwardly from the annular end face A as discussed hereinabove, the width of the labyrinth seal 54 as measured in a direction axially of the sealing device will decrease, accompanied by reduction in the capability of the labyrinth seal 54 to avoid the ingress of muddy water.
In the prior axle bearing 200 of the structure shown in FIG. 8 or FIG. 9, the outer peripheral surface of the inboard end of the inboard inner race 36, with which the bifurcated radial lips 38b and 38c of the seal lip member 38 are slidingly engaged, are exposed to the outside and is therefore easily contaminated by splashes of muddy water and dusts. For this reason, the outer peripheral surface of the inboard end of the inboard inner race 36, with which the bifurcated radial lips 38b and 38c of the seal lip member 38 are slidingly engaged, is susceptible to rusting. This is problematic in that once the outer peripheral surface of the inboard end of the inboard inner race 36 rusts, debris of rust detaching from such outer peripheral surface will accelerate wear of the bifurcated radial lips 38b and 38c, resulting in premature reduction in sealing performance.
In view of the foregoing, the present invention has for its essential object to provide an improved sealing device effective to make best use of a labyrinth seal to thereby increase the sealing performance.
To this end, the sealing device for a bearing according to one aspect of the present invention includes first and second annular sealing plates accommodated within an annular end space between inner and outer races, one of said first and second annular sealing plates being secured to one of the inner and outer races while the other of said first and second annular sealing plates is secured to the other of the inner and outer races, each of said first and second sealing plates being of a generally L-shaped section including a cylindrical wall and a radial upright wall, and an elastic seal lip element. The first sealing plate is secured with the radial upright wall thereof positioned adjacent respective end faces of the inner and outer races, and the radial upright wall of the first sealing plate has a free end remote from the cylindrical wall of the first sealing plate spaced a predetermined distance from the cylindrical wall of the second sealing plate to thereby form a radial gap. The radial upright wall of the first sealing plate also has an outer side face set back inwardly from a free end face of the cylindrical wall of the second sealing plate.
The amount of this set-back is so determined and so set that even in the presence of an error occurring during the manufacture or assemblage within the design tolerance, the set-back of the radial upright wall of the first sealing plate can necessarily occur. In other words, the amount of the set-back of the radial upright wall is chosen to be greater than the possible error which would occur during the manufacture or assemblage.
According to the above described structure, the labyrinth seal is formed in the radial gap delimited between the free end of the radial upright wall of the first sealing plate and the cylindrical wall of the second sealing plate, and the sealing capability against any possible ingress of muddy water can be obtained by the action of the labyrinth seal and the contact of the seal lips. Since in this structure the outer side surface of the radial upright wall of the first sealing plate is set back inwardly from the free end face of the cylindrical wall of the second sealing plate, the effective labyrinth seal having a predetermined width as measured in an axial direction can be maintained at all times between the radial upright wall of the first sealing plate and the cylindrical wall of the second sealing plate, thereby enhancing the sealing capability. Also, since set-back of the radial upright wall of the first sealing plate is sufficient relative to the free end face of the cylindrical wall of the second sealing plate, no complicated and time-consuming shaping process need be applied to the sealing plates, allowing the sealing plates of a simplified shape to be employed. Also, with no need to increase the size of the annular space for installation of the sealing device, the sealing capability can be increased.
In a preferred embodiment of the present invention, the elastic seal lip element may be provided in the second sealing plate.
If desired, the elastic seal lip element may include a side lip held in sliding engagement with the radial upright wall of the first sealing plate and at least one radial lip held in sliding engagement with the cylindrical wall of the first sealing plate. Where the elastic seal lip element includes the side lip and the radial lips, the side and radial lips cooperate with the labyrinth seal to define a multiple seal to thereby increase the sealing performance. Also, the presence of the side lip and the radial lips is effective to allow the seal lip that extends in either an axial direction or a radial direction to secure the sealing capability even when the first and second sealing plates displace relative to each other not only in an axial direction but also in a radial direction.
In a preferred embodiment of the present invention, an engagement surface of the second sealing plate that is secured to one of the inner and outer races may have at least a free end portion vulcanized with rubber. This rubber is the one integrated with the elastic seal lip element.
If the rubber is provided on the free end portion of the cylindrical wall of the second sealing plate as described above, any possible ingress of muddy water through the cylindrical wall of the second sealing place can be suppressed to secure a sufficient sealing capacity. Also, since this rubber is vulcanized, fixing thereof to the second sealing plate can easily and assuredly be accomplished.
In a preferred embodiment of the present invention, the first sealing plate may be secured to an outer peripheral surface of the inner race, in which case the second sealing plate is secured to an inner peripheral surface of the outer race.
Where the first and second sealing plates are so disposed, the position where the labyrinth seal is formed lies in the outer diameter region in the annular end space between the inner and outer races and a relatively large centrifugal force acts to enhance the sealing performance and, therefore, even though muddy water enters a space within the sealing device and extending from the labyrinth seal to the seal lip element, it can easily be drained off by the effect of the centrifugal force.
The sealing device according to another aspect of the present invention is for use with an axle bearing comprising an outer race having a fitting flange for connecting to an automobile body and also having an inner peripheral surface formed with dual outer raceways defined therein, first and second inner races juxtaposed to each other and each having an outer peripheral surface formed with an inner raceway in face-to-face relation to a corresponding one of the outer raceways, and two rows of rolling elements. The rolling elements of each row are accommodated in between one of the outer raceways of the outer race and the inner raceway of one of the inner races. In this bearing, the outer race has a width as measured in a direction axially thereof which is smaller than the sum of respective width of the inner races as measured in a direction axially thereof. At least an inboard-side end face of the outer race is positioned at a location set back inwardly towards an annular space, which is delimited between the outer race and the juxtaposed inner races, from an end face of one of the inner races.
The sealing device for use in that particular bearing is operable to seal the annular space at each of opposite ends of the annular space and includes a first sealing plate of a generally L-shaped section mounted on an outer peripheral surface of at least one of the juxtaposed inner races and positioned at a location adjacent one end of the inner races and having a radial upright wall formed therein, a second sealing plate mounted in an outer peripheral surface of the outer race and positioned at a location adjacent the first sealing plate and including an elastic seal lip member fixed to the second sealing plate. The elastic seal lip member is held in sliding engagement with the first sealing plate and has a bulged portion formed therewith and positioned spaced a slight distance radially from the upright wall of the first sealing plate to define a labyrinth seal between the bulged portion and the first sealing plate.
According to the second-mentioned aspect of the present invention, since any possible ingress of muddy water towards the sliding surface of the elastic seal lip member can be prevented by the effective labyrinth seal defined between the first sealing plate and the elastic seal lip member, rusting of the sliding surface can be prevented to secure a high sealing performance.
Preferably, the first sealing plate is mounted on at least an inboard-side outer peripheral surface of each of the juxtaposed inner races and the elastic seal lip member of the sealing device on an inboard side of the outer race is held in sliding contact with such first sealing plate. This is effective to protect the sliding surface on the inboard side that is susceptible to muddy water.
The elastic seal lip member may include bifurcated radial lips slidingly engaged with a cylindrical wall of the first sealing plate and a side lip extending slantwise radially outwardly from the elastic seal lip member and slidingly engaged with the radial upright wall of the first sealing plate. This is particularly advantageous in that the sealing performance can further be increased.
In a preferred embodiment, the outer race has an outer peripheral surface formed with a knuckle engagement. The knuckle engagement has a generally intermediate portion formed with a reduced-diameter step and wherein the second sealing plate is mounted on the reduced-diameter step of the knuckle engagement. Also, the juxtaposed inner races may be mounted directly on an outer race stem portion of a constant velocity joint and wherein the juxtaposed inner races are sandwiched and positioned in between a hub wheel for support of a wheel and a shoulder of a joint outer race of the constant velocity joint.